Devices and methods for treatment of vascular aneurysms

ABSTRACT

The present invention relates to devices and methods for the treatment of diseases in the vasculature, and more specifically, devices and methods for treatment of aneurysms found in blood vessels. In a first embodiment of the present invention, a two part prostheses, where one part is an expandable sponge structure and the other part is an expandable tubular mesh structure, is provided. In the first embodiment, the expandable sponge structure is intended to fill the aneurysm cavity to prevent further dilatation of the vessel wall by creating a buffer or barrier between the pressurized pulsating blood flow and the thinning vessel wall. In the first embodiment, the expandable tubular mesh structure is placed across the aneurysm, contacting the inner wall of healthy vessel proximal and distal to the aneurysm.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims the benefit of U.S.patent application Ser. No. 10/301,061, filed Nov. 20, 2002, whichclaims the benefit of U.S. Provisional Application No. 60/333,373, filedNov. 26, 2001.

BACKGROUND OF THE INVENTION

The present invention relates to devices and methods for the treatmentof diseases in the vasculature, and more specifically, devices andmethods for treatment of aneurysms found in blood vessels. Aneurysms canoccur in various areas of the cardiovascular system, but are commonlyfound in the abdominal aorta, thoracic aorta, and cerebral vessels.Aneurysms are unusual ballooning of the vessel due to loss of strengthand/or elasticity of the vessel wall. With the constant pulsatingpressure exerted on the vessel wall, the diseased or weakened wall canexpand out and potentially rupture, which frequently leads to fatality.Prior methods of treating aneurysms have consisted of invasive surgicaltechniques. The technique involves a major cut down to access thevessel, and the diseased portion of the vessel is replaced by asynthetic tubular graft. Accordingly, this invasive surgical procedurehas high mortality and morbidity rates.

Due to the inherent risks and complexities of the surgical procedures,various attempts have been made to develop minimally invasive methods totreat these aneurysms. For treatment of abdominal and thoracic aorticaneurysms, most of the attempts are catheter-based delivery of anendoluminal synthetic graft with some metallic structural memberintegrated into the graft, commonly called stent-grafts. One of theprimary deficiencies of these systems is durability of these implants.Because catheter-based delivery creates limitations on size andstructure of the implant that you can deliver to the target site, verythin synthetic grafts are attached to metallic structures, whereconstant interaction between the two with every heartbeat can cause wearon the graft. Also, the metallic structures often see significantcyclical loads from the pulsating blood, which can lead to fatiguefailure of the metallic structure. The combination of a thin fragilegraft with a metallic structure without infinite life capabilities canlead to implant failure and can ultimately lead to a fatality.

While the above methods have shown some promise with regard to treatingaortic aneurysms with minimally invasive techniques, there remains aneed for a treatment system which doesn't rely on the less than optimalcombination of a thin graft and metallic structural member to providelong-term positive results. The present invention describes variousembodiments and methods to address the shortcomings of current minimallyinvasive devices and to meet clinical needs.

SUMMARY OF THE INVENTION

In a first aspect, the present invention provides a two part prostheseswhere one part is an expandable sponge structure and the other part isan expandable tubular mesh structure. The expandable sponge structure isintended to fill the aneurysm cavity to prevent further dilatation ofthe vessel wall by creating a buffer or barrier between the pressurizedpulsating blood flow and the thinning vessel wall. The expandabletubular mesh structure, which is placed across the aneurysm contactingthe inner wall of healthy vessel proximal and distal to the aneurysm,serves two purposes. One, it defines the newly formed vessel lumen, eventhough it does not by itself provide a fluid barrier between the bloodflow and the aneurysm. Two, it keeps the expandable sponge structurefrom protruding out of the aneurysm and into the newly formed vessellumen. The expandable tubular mesh structure is delivered first acrossthe aneurysm. Then, the expandable sponge structure is delivered via acatheter-based delivery system through a “cell” of the tubular meshstructure and into the aneurysm sac. When the sponge structure isdeployed into the aneurysm sac and comes in contact with fluid, it willexpand to a size larger than the largest opening or cell of the tubularmesh structure as to prevent the sponge structure from getting out ofthe aneurysm sac. The filled aneurysm sac will most likely clot off andprevent further dilation of the aneurysm and subsequent rupture. Theblood flow should maintain a natural lumen where the luminal diameter isapproximately defined by the diameter of the tubular mesh structure. Theadvantage of this system is that the sponge filler material acts like agraft but has unparalleled durability. The metallic structure can beoptimized for durability as well because the size constraint is somewhatrelieved due to the absence of an integrated graft material, which takesup a significant amount of space in a catheter.

In addition, the expandable sponge structure can be used to repairexisting endoluminal stent-grafts which have developed leaks. There arethousands of endoluminal stent-grafts implanted into humans to treatabdominal aortic aneurysms. That number is growing daily. Theendoluminal stent-grafts are intended to exclude the aneurysm from bloodflow and blood pressure by placing a minimally porous graft supportedfully or partially by metallic structural members, typically calledstents. The acute success rate of these devices is very high, but thereare a significant number of these which develop leaks, or bloodflow/pressure re-entering the aneurysm sac, some time after theprocedure. If the source of the leak can be accessed by the deliverysystem, the expandable sponge structure can be deployed through thataccess point.

In another aspect, the present invention provides an inflatable tubularballoon graft. It is a tubular graft, straight or bifurcated, where itswall is not a solid structure but a hollow chamber. The chamber can befilled with a variety of materials which can dictate the mechanicalproperties of the prostheses. The unfilled tubular balloon graft can befolded and loaded into a catheter-based delivery system, and once inposition the tubular balloon graft can be “inflated” with the fillermaterial. The material would be filled in a fluid form and may stay afluid form or can be solidified by various means such as UV light, heat,and time. The advantage of this system is that a metallic structure isnot needed to provide structure to the graft. It is instead replaced bythe injectable fluid within the chamber of the tubular balloon graft.Customization of the mechanical properties of the graft is easilyaccomplished by using balloon fillers of varying properties.

The tubular balloon graft can be completely non-porous, completelyporous with same degree of porosity throughout the graft, completelyporous with varying porosity within the graft, or partially non-porousand partially porous. Significant porosity on the very outer layer wouldallow for delivery of an aneurysm sac filling substance or a drug.Porosity on the ends of the graft will help promote cellular in-growth.Porosity on the ends can also be used to deliver an adhesive so that thegraft can be securely attached to the vessel wall.

Another embodiment of the tubular balloon graft includes a tubularballoon graft with a bulging outer layer. This will allow the outersurface of the tubular balloon graft to fill some or all of theaneurysm. This will provide a primary or secondary barrier for theaneurysm wall from the pulsating blood flow and will provide a means toprevent migration of the graft due to the enlarged area within thegraft. An alternate method of construction would be to attach a bulgingouter skin to a standard tubular thin-walled graft and provide a portfor injection of the filler substance. Alternatively, instead of abulging outer skin, a very compliant outer skin can be used so that thevolume of material is minimized. The compliant outer skin would be ableto expand at very low inflation pressures that would be non-destructiveto the aneurysm wall.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates the two-part prosthesis.

FIG. 1B illustrates a bifurcated version of the expandable tubular meshstructure and the expandable sponge structure.

FIG. 1C illustrates an expandable tubular mesh structure placed acrossan aneurysm and the expandable sponge structure filling up the aneurysm.

FIGS. 2A-2C illustrate the various cross-sections of the expandablesponge structure.

FIG. 3A illustrates a long continuous sponge structure.

FIG. 3B illustrates multiple short sponge structures.

FIG. 4 illustrates the catheter-based delivery system.

FIG. 5 illustrates a curved delivery catheter.

FIG. 6 illustrates a method of ensuring that the delivery catheter's tipstays inside the aneurysm sac.

FIG. 7A illustrates an expandable basket-like structure.

FIG. 7B illustrates an expandable braid-like structure.

FIGS. 8 and 9 illustrate expandable tubular mesh structures.

FIG. 10 illustrates a delivery catheter tracked over a guidewire andplaced in a stent-graft which developed a leak.

FIG. 11 illustrates the sponge delivered through the delivery catheter.

FIGS. 12-15 illustrate tubular balloon grafts.

FIGS. 16 and 17 illustrate tubular balloon grafts being expanded.

FIG. 18 illustrates a tubular balloon graft.

FIGS. 19, 20A and 20B illustrate a vascular graft with an integratedtubular balloon.

FIGS. 21A-21E illustrate a method of delivering a graft with an externalballoon.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1A shows the two-part prosthesis comprising of an expandablesponge structure 1 and an expandable tubular mesh structure 2 placed inan abdominal aortic aneurysm 3 located in the infra-renal aorta notinvolving the iliac arteries. FIG. 1B shows a bifurcated version of theexpandable tubular mesh structure 2 and the expandable sponge structure1 in an abdominal aortic aneurysm located in the infra-renal aorta andinvolving both iliac arteries. FIG. 1C shows an expandable tubular meshstructure 2 placed across an aneurysm commonly found in cerebralarteries and the expandable sponge structure 1 filling up the aneurysm.The expandable sponge structure 1 is placed through the expandabletubular mesh structure 2 into the aneurysm, filling up the aneurysmalsac which provides a barrier between the thin fragile wall of theaneurysm and the pressurized pulsating blood. The tubular mesh structure2 keeps the expanded sponge 1 within the confines of the aneurysm andaway from the flow path.

The expandable sponge structure 1 is preferably made of common medicalgrade polymers or natural substances like collagen which can bemanufactured into a sponge structure. The sponge structure can beprocessed in such a way so that it can be compressed to a dry conditionsize substantially smaller than the wet condition size, exhibiting hugeexpansion ratio. The expanded sponge structure can take various forms.FIGS. 2A-2C show the various expanded cross-sections that the expandablesponge structure 1 can be. FIG. 2A shows a circular cross section, FIG.2B shows a square cross section, and FIG. 2C show a triangular crosssection. Any cross section can be used. The most important requirementis that it cannot escape from the aneurysm sac through a cell of theexpandable tubular mesh structure 2. The length of the expandable spongestructure 1 can vary as well. FIG. 3A shows a long continuous structure1. And FIG. 3B shows multiple short structures 1.

One method of delivering the sponge filler 1 into the aneurysm sac isshown by the catheter-based delivery system in FIG. 4. The catheter 4can hold the compressed sponge 1 within its lumen, and when pushed outwith the plunger 5 into the blood filled aneurysm sac, the sponge willexpand out to a substantially larger size. The expanded size of thesponge filler is preferably larger than the largest opening of thetubular mesh structure as to prevent the sponge from escaping theaneurysm sac. FIG. 5 shows an example of a curved delivery catheter 4,where the tip is placed through a cell of the tubular mesh structure 2and the expandable sponge structure 1 is being deployed into theaneurysm sac. It is important that the tip of the delivery catheter isthrough a cell of the tubular mesh structure into the aneurysm becausethe expandable sponge will expand very quickly after being exposed tothe blood and being unconstrained by a catheter. FIG. 6 shows a methodof ensuring that the delivery catheter's 4 tip stays inside the aneurysmsac by having a balloon 6 on the tip of it, and when inflated after thetip is within the aneurysm sac it will prevent the catheter tip frombacking out of the aneurysm sac. FIG. 7A shows an expandable basket-likestructure 7 and FIG. 7B shows an expandable braid-like structure 8 whichare alternatives to having a balloon 6 on the tip of the catheter 4.

The expandable tubular mesh structure 2 can be made of a metal or of apolymer. The versions made of a metal can be self-expanding from asmaller compressed state or balloon expandable from a smaller compressedor as-cut state. The self-expanding version may be made of metals whichexhibit large amounts of elasticity (i.e. nickel-titanium, spring steel,MP-35N and elgiloy) such that when they are compressed down from theirexpanded state to the compressed state to load into a delivery catheter,they will substantially return to their expanded condition when releasedfrom the catheter. Alternatively, shape memory metals likenickel-titanium can be used to provide large expansion ratios. Theballoon expandable version may be made of metals which exhibit largepermanent deformations without significantly compromising the mechanicalperformance. The following are some common medical grade metals whichare well suited for this purpose: stainless steel, titanium, tantulum,and martensitic nickel titanium. In either the self-expanding or theballoon expandable case, the intent is to deliver the expandable tubularmesh 2 to the target site in a smaller or compressed condition via acatheter-based delivery system so that the target site can be accessedthrough a remote vascular access point which is conducive to apercutaneous or minimally invasive approach.

The expandable tubular mesh structure 2 shown in FIGS. 1A, 1B, 1C, 5,and 6 represent a generic mesh structure. FIG. 8 shows an expandabletubular mesh structure where long continuous struts 9 are connected toanchoring end members 10. This allows the structure to be very low inprofile in the compressed state, and the durability of this type ofstructure can be optimized because no radial element exists in thelongitudinal struts 9. FIG. 9 show an alternate expandable tubular meshstructure preferably made from a polymer such as PTFE, Polyester,Polyurethane, and the like. The structure has relatively large holes 11to give access to the expandable sponge delivery catheter. The endsincorporate an anchoring member 12, either self-expanding or balloonexpandable.

FIG. 10 shows a delivery catheter 4 which has been tracked over aguidewire 14, which has been placed into the aneurysm sac through anopening 15 of an existing endoluminal stent-graft 13 which developed aleak. The balloon 6 on the delivery catheter 4 was inflated after thedelivery catheter 4 was positioned within the aneurysm sac. FIG. 11shows the guidewire 14 removed, and the expandable sponge structure 1being delivered through the delivery catheter 4.

FIG. 12 shows a section view of a tubular balloon graft 19 positionedacross an infra-renal aortic aneurysm blocking off the flow to theaneurysm sac. The tubular balloon graft's 19 wall is made of an innerwall 16, an outer wall 17 and a chamber 18 between them. The chamber 18can be filled with various materials to dictate the mechanicalproperties of the prosthesis. FIG. 13 shows a bifurcated tubular balloongraft 20 positioned across an infra-renal aortic aneurysm withbi-lateral iliac involvement.

The tubular balloon implant can be made of the various biocompatiblematerials used to make balloon catheters. Those materials include P.E.T.(Polyester), nylon, urethane, and silicone. It can also be made of otherimplant grade materials such as ePTFE. One method of making such adevice is to start with two thin walled tubes of differing diameters.The difference between the diameters of the tubes will dictate thevolume of the balloon chamber. The ends of the tubes can be sealedtogether with adhesive or by heat to form the balloon chamber. Acommunication port will be necessary to be able to fill the port withthe injected material.

The injected material can be an epoxy, a UV-curable epoxy, silicone,urethane or other type of biocompatible materials such as albumin,collagen, and gelatin glue which is injected into the balloon, and thencured in situ. Or, the injected material doesn't necessarily have to becured. The as-delivered state may provide the appropriate mechanicalproperties for the application. Therefore, substances like sterilesaline, biocompatible oils, or biocompatible adhesives can be left inthe tubular balloon in the as-delivered state.

The tubular balloon graft can be non-porous to very porous. FIG. 14shows a version where the tubular balloon graft has a porous outer wall24. The chamber 21 of the tubular balloon graft can be used to deliveran aneurysm sac filling substance such as UV curable adhesive 22. Theholes 23 which dictate the porosity of the tubular balloon graft can becreated with laser drilling, etching, and other methods. The porositycan be varied in select areas of the graft. FIG. 15 shows a tubularballoon graft with only the ends of the graft have porosity to eitherpromote cellular in-growth or to inject an adhesive which allows secureattachment of the graft ends to the vessel wall.

FIG. 16 shows a tubular balloon graft 19 which is being expanded from afolded condition (not shown) by a balloon catheter 25. Once expanded,the chamber 18 of the tubular balloon graft 19 can be filled with thedesired substance through the chamber access port 26. FIG. 17 shows atubular balloon graft 19 being expanded by an inflation process orfilling the chamber 18 of the tubular balloon graft 19 through thechamber access port 26.

FIG. 18 shows a version of the tubular balloon graft with an outer wall17 which is substantially bulged out so that it fills some or all of theaneurysm sac. FIG. 19 shows a vascular graft 27 which has an integratedballoon 28 attached to the outside surface of the graft. The balloon canbe pre-bulged and folded down for delivery, or it can be a verycompliant material like silicone, urethane, or latex so that it has nofolds whether compressed or expanded. FIG. 20A shows the same type ofimplant, a graft 27 with an external balloon 28, used in a cerebralvessel aneurysm 29. FIG. 20B show the same implant as 20A, except thatthe implant balloon does not fully fill the aneurysm, which can beacceptable because the graft 27 excludes the aneurysm from the bloodflow, and the primary purpose of the balloon 28 is to prevent migrationof the graft 27.

The graft 27 can be made of commonly used implant polymers such as PTFE,Polyester, Polyurethane, etc. The balloon 28 surrounding the graft canbe made of the same commonly used vascular implant materials as well.The graft and balloon materials can be different, but it is commonlyknown that using the same material for both would facilitateprocessing/manufacturing. The theory is that the balloon 28 wouldpreferentially only deploy into the aneurysm sac where the resistance toexpansion is minimal as compared to the vessel wall. The graft 27 wouldprovide the primary barrier between the pressurized blood and the thinwall of the aneurysm. Secondarily, the balloon itself provides a bufferfrom the pressurized blood. The balloon's 28 primary function, however,is to hold the graft 27 in place. Since the expanded section of theimplant is “locked” into the aneurysm, the graft 27 should not migrate.Also, the balloon 28, in the filled state, will provide hoop strength tothe graft 27.

FIGS. 21A-21E demonstrate one method of delivering a graft with anexternal balloon to the target site. FIG. 21A shows the implant loadedonto a balloon delivery catheter 30 with an outer sheath 32 andpositioned over a guide wire 31 at the aneurysm target site. FIG. 21Bshows that once in position, the outer sheath 32 is withdrawn. FIG. 21Cshows the balloon delivery catheter 33 being inflated, pushing theimplant 34 against the healthy vessel walls on both sides of theaneurysm. FIG. 21D shows that the balloon delivery catheter 30 may alsohave an implant balloon inflation port 35 which can now be used to fillup the implant balloon 28 with a biocompatible substance. The substancecan be sterile saline, contrast agent, hydrogel, and UV cure adhesive toname a few. Most likely, low inflation pressures would be used to fillthe implant balloon 28. FIG. 21E shows that once the implant balloon 28is filled, the implant balloon inflation port 35 can be detached and thedelivery catheter 30 removed.

1. A method for treating an aneurysm, said method comprising:positioning at least one double-walled filling structure across theaneurysm; filling at least one filling structure with a fluid fillingmedium so that an outer wall conforms to the inside of the aneurysm andan inner wall forms a generally tubular lumen to provide for blood flow:supporting the tubular lumen while and/or after the filing structure isbeing filled; hardening the filling medium while the tubular lumenremains supported; and removing support after the filling material hashardened.
 2. A method as in claim 1, wherein the tubular lumen supportextends upstream and downstream from the double-walled filling structureso that tubular support aligns and conforms each end of the fillingstructure with the blood vessel.
 3. A method as in claim 1, wherein atleast an outer wall of the filling structure is formed from anon-compliant material.
 4. A method as in claim 3, wherein substantiallythe entire filling structure is formed from a non-compliant material. 5.A method as in claim 3, wherein the tubular support comprises aninflatable support balloon having a compliant structure.
 6. A method asin claim 3, wherein the tubular support comprises a mechanical structureexpandable to one or more fixed diameters.
 7. A method as in claim 1,further comprising positioning an anchor or sealing element of at leastone opening from the tubular lumen of the filing structure to a lumen ofthe blood vessel.
 8. A method as in claim 7, further comprisingpositioning an anchor or sealing element at each opening.
 9. A method asin claim 1, wherein the filling material comprises a flowable polymerwhich is curable in situ.
 10. A method as in claim 9, wherein thepolymer comprises a polyurethane or a collagen.
 11. A method as in claim9, wherein the filling material comprises a two-part part curablematerial which hardened after mixing.
 12. A system for treating ananeurysm, said system comprising: at least one double-walled fillingstructure having an outer wall and an inner wall, wherein the fillingstructure is adapted to be filled with a hardenable fluid filling mediumso that the outer wall conforms to the inside surface of the aneurysmand the inner surface forms a generally tubular lumen to provide bloodflow; and a delivery catheter having an expandable tubular support whichcan be positioned within the tubular lumen to carry the double-walledfilling structure.
 13. A system as in claim 12, wherein the expandabletubular support extends upstream and downstream from the double-walledfilling structure so that tubular support aligns and conforms each endof the filling structure with the blood vessel.
 14. A system as in claim12, wherein at least an outer wall of the filling structure is formedfrom a compliant material.
 15. A system as in claim 12, whereinsubstantially the entire filling structure is formed from a compliantmaterial.
 16. A system as in claim 12, wherein the tubular supportcomprises an inflatable support balloon having a non-compliantstructure.
 17. A system as in claim 16, wherein the tubular supportcomprises a mechanical structure expandable to one or more fixeddiameters.
 18. A system as in claim 12, wherein at least a portion of anexterior surface of the filling structure is modified to enhance sealingor tissue ingrowth.